1. Field of the Invention
The invention relates to the field of integrated circuits. More specifically, maintaining compatibility between circuit components when functions are moved from one circuit to another.
2. Prior Art
FIG. 1 illustrates two circuit elements. An integrated circuit, cell 10 and a circuit element 14 having an integrated circuit transceiver 11 and a transformer 12. Both circuit 10 and element 14 are typically mounted on a printed circuit board and are interconnected by traces on the board represented by the lines 15, 16 and 17. More specifically, the cell 10 in one embodiment is a xe2x80x9cNeuron(copyright)xe2x80x9d chip manufactured under license by Toshiba, part no. TMPN 3150/3120. This cell is also described in U.S. Pat. No. 4,918,690. Cells are used at nodes in a network having distributed intelligence and, for instance, receives inputs at one node to control an appliance at another node. For the configuration shown in FIG. 1, the cells are connected through circuit elements 19 in a network having a twisted pair line as the common link between the nodes. Input and output signals for control of devices are coupled over lines 18 including power for cell 10.
The transceiver 11 drives a signal onto and receives a signal from the twisted pair 19 through the transformer 12. Power for the embodiment of FIG. 1 is shown coupled to the circuit element 14. (In other embodiments power is obtained directly from the twisted pair 19 in the so-called xe2x80x9cphantom fedxe2x80x9d configuration.) The circuit element 14 is commercially available and is referred to as a flexible topography transceiver (FTT) from Echelon Corporation, FTT10A, model no. 50051.
At the time the cell 10 and transceiver 11 were initially designed it was cost effective to provide two separate integrated circuits. Now it is more economic to fabricate the transceiver 11 on the same substrate as the cell 10. However, if this is done existing circuit board designs made to accept the cell 10 and circuit element 14 may not be used. Moreover, in some instances the cell 10 is used without the transceiver 11 and it would appear that two separate parts are required to be stocked if the transceiver is fabricated as part of the cell.
As will be seen, the present invention allows the transceiver to be incorporated within the cell 10. This is done without any design changes to circuit boards and additionally, allows the newly configured cell to be used with and without the transceiver with the new cell having the same xe2x80x9cfootprintxe2x80x9d as the earlier cell.
An improved combination of a cell and transceiver is described. An integrated circuit having a cell, a transceiver, a multiplexer and a programming circuit incorporated thereon is fabricated. The multiplexer is used to couple two output terminals of the integrated circuit either to a pair of lines from the transceiver or a pair of lines from the cell as a function of a stored state in the programming circuit. A second circuit element is used having a transformer. When the bit in the integrated circuit is set to one state the pair of terminals from the integrated circuits connects the transformer directly to the transceiver providing the same result as shown in FIG. 1.